Moisture and cold aren't a good mix -- and it's not uncommon to have a vehicle's door locks freeze after a winter carwash or after a spate of damp warm weather that's followed by a cold snap. Many have dealt with this pesky problem simply by heating up their car key to thaw out the frozen lock mechanism.

"And that's the worst thing you can do," says Pat Goss, master technician of PBS' "MotorWeek." "The only safe way to unfreeze a lock is to use an alcohol-based product, like Lock De-Icer."

Keys on modern cars have transponders built into them. If you heat such a key, you will damage the electronic component, Goss says. "Then you'll have to get a new key and have the system reprogrammed, and that can cost you anywhere from $85 to as much as $500 if you happen to own an expensive, high-line car."

Frozen locks are an indication that the lock mechanism isn't properly lubricated and protected from penetrating moisture. Goss says all car locks should be lubed with a graphite-based lubricant several times a year and immediately after using any alcohol-based lock de-icer.